Overview and Basis of Presentation - Impact of Adopting ASU 2017-07 on Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Corporate activities		$ 3,777	$ 4,425	$ 8,529	$ 9,886
Other expense	[1]	527	248	1,308	922
As Previously Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Corporate activities			4,474		10,092
ASU 2017-07
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Corporate activities			(49)		(206)
Other expense			248		922
Services
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products		254,638	245,757	792,775	808,304
Services | As Previously Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products			254,963		813,456
Services | Reclassifications to Conform with Revenue Presentation
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products			(9,007)		(4,436)
Services | ASU 2017-07
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products			(199)		(716)
Products
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products		$ 46,974	46,077	$ 122,529	121,508
Products | As Previously Reported
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products			37,070		117,072
Products | Reclassifications to Conform with Revenue Presentation
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Cost of services and products			$ 9,007		$ 4,436

[1] We adopted ASU 2017-07 on January 1, 2018, which requires retrospective adoption. As a result, we recorded the nonservice cost component of net periodic benefit cost within other expense for the three and nine months ended September 30, 2018, and we reclassified $0.2 million from operating expenses to other expense for the three months ended September 30, 2017 and $0.9 million for the nine months ended September 30, 2017 to conform with current period presentation. Refer to Note 1 – Overview and Basis of Presentation for additional details on the impact of this adoption on our Condensed Consolidated Statements of Operations.